Accelerometer Measurement

Accelerometer measurement

As one of the measurement parameters, stereophile always publish their data of accelerometer measurement on every speaker they tested. I always though that you need expensive equipment to achieve that. Not until I come across this article

http://www.libinst.com/accel.htm

Well, the hardware is reasonable and the investment is not that high. Good to know how my equipment vibrates under high sound pressure! So, right on to digikey and got the parts

It only took 3 days to arrive home. Neat and tidy! Since I use ULN-8 I still need to make a balanced (XLR) to unbalanced (BNC) connection. Well, easy enough to do. Setting up the MIO on my ULN-8 is the hardest part and I toke a good 30 min to work out the logic behind!

I did my first test on my sound card which is placed outside my computer box connected by optical fibre. The sound card is individually powered by its own linear power supply. You can get all the details on my other pages. Here is the result

First the yellow line – no spikes, no air con, speaker turn off

You can see the the noise floor is quite low and all the high frequency noise is not there. Well, the speaker is off!. You can also see the noisy area corresponds to 120Hz, 110 Hz and 100Hz. I think this must be coming from the transformer as the main frequency out from PPP is 60Hz. But I am not sure why 100Hz and 120 Hz is there!?

The red line – with spike, no air con

this should have been the second best, but when I did the measurement, the escalator outside my home is moving!!

Green- no spike, air con on

Blue – with spike, air con on

Now you can see the clearly the effect of spike on the body vibration!!!

More testing to do in the future